This application claims the priority of German application 198 26 538.7, filed in Germany on Jun. 15, 1998, the disclosure(s) of which is (are) expressly incorporated by reference herein.
The invention relates to a collapsible bicycle. Preferred embodiments of the invention relate to collapsible bicycles of the type comprising a forward frame part with a steering device for a front wheel and a rearward frame part with a rear wheel, and a connection between the forward and the rearward frame part including a turning knuckle swivellable about a transverse axis of the bicycle, wherein the steering device includes a fork which carries the front wheel, two fork tubes and one fork bridge, a handle bar and a steering tube connecting the handle bar and the fork bridge.
German Patent Document DE 37 01 803 A1 describes such a bicycle, in the case of which the frame includes a forward frame part with a steering device for a front wheel and of a rearward frame part with a rear wheel, a connection between the forward and the rearward frame part being formed at least by a turning knuckle which can be swivelled about a transverse axis of the bicycle. The transverse axis is congruent with the bottom bracket bearing. The steering device includes a fork which carries the front wheel and includes two forked tubes and a fork bridge, a handle bar and a handle bar tube connecting the handle bar and the fork.
For collapsing the bicycle, the front wheel as well as the rear wheel are removed. It will then be possible to swivel the rearward frame part with the swing arm rear suspension about the axis of rotation, which coincides with the bottom bracket bearing, toward the front. In addition, for reducing the packing dimension, the handle bar can also be rotated by 90.degree., the front wheel fork maintaining its position. For this purpose, the rigid connection of the handle bar and the front wheel handle must be released which has the effect that, when the bicycle is built together, the front wheel and the handle bar must in each case be adjusted to one another. In addition, the expenditures for collapsing the bicycle become very large because both wheels must be removed, which again has a negative effect on the packing dimension of the collapsed bicycle.
It is an object of the invention to design a collapsible bicycle such that, during the collapsing and in the collapsed condition of the bicycle, the rear wheel can remain mounted in the rear wheel fork, that a packing dimension is achieved which is as small as possible, and that expenditures of labor occur which are as low as possible when, from the collapsed bicycle, a bicycle is to be produced which can be ridden.
According to the invention, this object is achieved by providing a bicycle of the above-mentioned type, wherein the steering device and connection are configured such that, at an angle of lock of the steering device of approximately ninety degrees, a distance exists between the fork tubes and a bicycle center plane which permits the swivelling-along of the rear wheel during the swivelling of the rearward frame part about the transverse axis, without any contact with the fork tubes.
According to the invention, the bicycle is designed such that, in the case of an angle of lock of the steering device of ninety degrees, a distance exists between the fork tubes and a bicycle center plane which permits the swivelling-along of the rear wheel during the swivelling of the rearward frame part about the transverse axis, without any contact with the fork tubes.
Thus, during the swivelling of the rearward frame part, the rear wheel can advantageously remain mounted in the rear wheel fork. In this case, when the bicycle is collapsed, the rearward frame part is swivelled about the transverse axis of the bottom bracket bearing until it comes to rest, for example, on a lower frame tube of the bicycle frame. For this purpose, it is necessary according to certain preferred embodiments that the steering device is steered with an angle of steering lock of approximately 90.degree.. This advantageously reduces the packing dimension because the handle bar extends in the longitudinal direction of the bicycle and thus a very small packing dimension occurs in the transverse direction of the bicycle.
In a preferred embodiment of the invention, the distance between the fork tubes and the bicycle center plane in the case of an angle of lock of the steering device by 90.degree. is achieved by the design of the fork bridge. This fork bridge forms a connection between the fork tubes and the steering tube with an offset between their longitudinal axes. In a position of the steering device for straight-ahead riding, this offset is preferably directed in the longitudinal direction of the bicycle. As a result, the distance which is required for the swivelling-in of the rear wheel to its contact on the lower frame tube advantageously occurs automatically during the steering of the steering device at an angle of lock of 90.degree..
In another preferred embodiment of the invention, the steering tube and/or the fork bridge are supported by a spring device and/or a damper device on the frame. As a result, a resilient front wheel suspension for a collapsible bicycle is advantageously achieved which has a very stable construction if the frame and the steering device are connected with one another by a longitudinal control arm.